The present invention relates to a data processing apparatus capable of efficiently performing the protection of data and the processing of data.
In image processing apparatuses having a copy function of scanning a manuscript image and thereby copying the image, integration of functions is progressing in recent years. Some of presently available image processing apparatuses have a plurality of functions in addition to the copy function. These additional functions include: the function of a network printer which is connected to a communication network such as a LAN, and which receives image data from an external device such as a personal computer (PC) and then outputs the image; and a facsimile function for transmitting and receiving image data to and from an external facsimile machine by means of facsimile communication. Such an image processing apparatus comprises storing means such as a hard disk or a semiconductor memory for temporarily storing image data to be processed. In the image processing apparatus, the storing means sequentially stores inputted image data, while each piece of the image data stored in the storing means is processed at an appropriate time that the piece of image data should be processed. As such, a large amount of image data is processed efficiently without stagnation.
After being processed by the image processing apparatus, the image data is maintained in a state stored in the storing means until the data is overwritten when the storing means stores new image data. In some cases, in the copying of manuscript images or the outputting of images, image data processed by the image processing apparatus can contain information having confidentiality such as a document describing personal information or trade secrets. When such image data containing confidential information is stored for a long time in the storing means of the image processing apparatus, a risk arises that the image data stored in the storing means could be retrieved in an unauthorized manner so that the information could leak out. Then, a technique is necessary that prevents the image data from being retrieved in the storing means in an unauthorized manner. Japanese Patent Application Laid-Open No. 9-284572 (1997) discloses a technique in which when the processing of image data is completed, the image data stored in storing means is deleted or alternatively overwritten with another data so that the retrieval of the image data is made impossible. As such, an image processing apparatus has been developed that nullifies image data by means of deletion or overwrite and thereby protects image data from unauthorized use.
In such an image processing apparatus that nullifies image data by means of deletion or overwrite, the nullification of image data needs a time proportional to the data size of the image data. Further, during the nullification of image data, the processing of other image data becomes stagnated or even impossible. Thus, in case that image data to be processed is received continuously, the image processing apparatus has the problem of a decrease in the throughput of the image data.